Sharpening device for rotary knives



Dec. 27, 1955 N. J. RlTZERT 2,728,176

SHARPENING DEVICE FOR ROTARY KNIVES Filed June 5, 1952 INVENTOR. NORMAN J. R ITZERT ited States Patent SHARPENTNG DEVICE FOR ROTARY KNIVES Norman J. Ritzert, Dayton, Ohio, assignor to The Dayton Rubber Company, a corporation of Ohio Application June 5, 1952, Serial No. 291,844

4 Claims. (Cl. 51-246) This invention relates to an abrasive type of knife sharpener and, more particularly, to a device for sharpening rotary knives of the'type used on belt-cuttrng machines.

In the manufacture of V-belts, it is common practice to first form a belt sleeve which is thereafter cut up into V-belts by means of rotary knives which cut the individual belts from the end of the sleeve. The cutting edges of the belt-cutting knives become dull in a very short time due to the continuous cutting action of the knives on the rubber and fabric composition from which the sleeve is formed. Hence, frequent re-sharpening of the knives is necessary to insure that the belts cut from the sleeve will have smooth, clean-cut edges. Heretofore this has been accomplished by removing the knives from the machine and regrinding the cutting edges thereof so as to restore the knives to their original, sharpened condition.

To eliminate the need of removing the dulled knives from the belt-cutting machine for the purpose of resharpening them, I have contrived a knife sharpening device which is mounted directly on the belt-cutting machine and operates to continually grind and sharpen the cutting edge of the belt cutting knife as the machine operates. This sharpening device is comprised of a pair of abrasive elements which are set at an angle to one another so as to form a beveled cutting edge on the edge of the knife. A motor device is provided for oscillating the abrasive elements back and forth along the cutting edge of the knife, as the latter rotates, thereby providing a whetting action of the elements on the edge of the blade. Hence, the knife will be continually re-sharpened as the machine operates to cut V-belts from the belt sleeves, and will always be maintained in a perfectly sharpened condition thereby improving the quality of the V-belts produced by the machine.

Accordingly, it is an object of the present invention to provide a device for sharpening the rotary knives of a belt-cutting machine while the machine is in operation and the knives are rotating.

Another object of the invention is to provide an abrasive type of sharpening device for grinding both sides of the cutting edge of a rotary belt-cutting knife.

Another object of the invention is to provide means for oscillating the abrasive sharpening device back and forth along the cutting edge of the knife, as the latter rotates, thereby whetting the edge of the knife blade to form a keen cutting edge thereon.

Another object of the invention is to provide an oscillatory device for sharpening the knife of a. belt-cutting machine in which a pair of abrasive elements are so mounted on the oscillatory member as to be resiliently pressed against both sides of the cutting edge simultaneously.

Another object of the invention is to provide an automatically reversible, fluid-pressure motor for oscillating the abrasive elements of a rotary knife sharpening device.

With these and other objects in view which will become apparent from the following description, the invention includes certain novel features of construction and combinations of parts, the essential elements of which are set forth in the appended claims and a preferred form or embodiment of which will hereinafter be described with reference to the drawings which accompany and form a part of this specification.

In the drawings:

Figure 1 is a side elevation of a preferred form of my invention. a

Figure 2 is an end view of the device shown in Figure 1.

Figure 3 is a cross-sectional view taken along the line 3-3 of Figure 2.

The device shown in Figures 1 to 3 of the drawings.

illustrates one form of my invention, although it is to be realized, of course, that there are various other forms of mechanisms which could be used to successfully carry out my invention. However, the device shown in the present drawings has been found to give excellent results and is, therefore, the embodiment which I prefer to show for the purpose of illustrating the principles of my invention.

In Figure 1, there is shown a belt-cutting knife 10 which is secured to a shaft 11 which may be rotated at suitable speed from the power source for the belt-cutting machine. As shown herein, the knife 10 is circular and is provided on its periphery with a cutting edge 12 formed by beveled faces 13 and 14 provided on opposite sides of the blade.

To maintain the cutting edge 12 in a continuously sharpened condition while it is being operated to cut V-belts from the end of a belt sleeve, abrasive stones 15 and 16 are mounted so as to lie at an angle to one another as shown in Figure 2. The angularity of the stones 15 and 16 is such as to cause the beveled faces 13 and 14 of the knife to be ground at the proper angle of inclination to provide a cutting edge 12 of desired acuteness.

The stones 15 and 16 are clamped to the lower ends of arms 17 and 18, respectively, by means of angle clamps 19 and 20 which are tightened against the stones by screws 21. The arms 17 and 18 are supported on a block 25 which is fastened to one end of a shaft 26. As shown in Figure l, the upper ends of arms 17 and 18 are received within elongated slots provided on opposite sides of the block 25. They are held in place within the blocks by means of pivot bolts 27 which are received within the block 25 and which pass through apertures provided in the upper ends of the arms 17 and 18. Hence, the arms are able to pivot about the bolts 27 and may be swung outwardly from the position shown in Figure 2 to cause the stones 15 and 16 to approach one another and to bear against the beveled faces 13 and'14 of the knife 10. A spring 56 or other suitable means (not shown) may be provided for yieldably urging the arms to swing outwardly on their pivots 27, thereby to resiliently press the stones against the opposite sides of the knife. As shown in Figures 1 and 2, compression spring 56 is seated at one end in a recess 57 shown in dotted lines in block 25, and bears at the other end against a projection 58 on member 17. This tends to urge abrasive member 15 into engagement with the knife. A similar spring arrangement is provided for pivoted member 18 on the opposite side.

For the purpose of providing a whetting action of the stones against the cutting edge of the knife, means is provided for oscillating the shaft 26 and causing the stones to wipe back and forth along the cutting edge. As shown herein, this means includes a fluid pressure cylinder 30 which is fitted with a pair of pistons 31 and 32 (Figure 3) which are connected together for joint operation by a bar 33. This bar is provided with a rack 34 which meshes with a gear pinion 35 secured to the shaft 26. Hence, as the pistons 31 and 32 are shuttled back and forth within the cylinder 30, the rack 34 will oscillate the pinion 35, the shaft 26, and the block 25 on which the stones 15 and 16 are supported.

Automatic reciprocation of the pistons 31 and 32 Within the cylinder 3% is effected by a reversing valve 40 which is supported by straps 41 attached to the cylinder 30. The valve 40 is provided with a spool 42 which is slidable Within a bore provided in the valve 40. The spool 42 is operated at the end of each reciprocation of the pistons 31 and 32 by an operating slide 43 having arms 44 adapted to engage the ends of the spool 32. The slide 43 is connected to the bar 33 by a post 45 which is slidable within a slot 46 provided in the cylinder 30. Hence, as the pistons 31 and 32 approach the end of their movement in either direction, one of the arms 44 will contact the end of the spool 42 associated therewith, and slide the latter within the valve and reverse the fluid connections to the cylinder 39.

Fluid under pressure for operating the pistons 31 and 32 is supplied to the valve 40 through a fluid pressure line 50. The line d communicatees with a bore provided in the valve 49 having two branches 51 and 52. When the spool 42 is in the position shown in Figure 3, fluid under pressure from the branch 51 will be communicated with a line 53 which is connected to the righthand end of the cylinder 3i). Hence, fluid under pressure will be admitted to the right-hand end of the cylinder and the pistons 31 and 32 will be moved toward the lefthand end or" the cylinder. The left-hand end of the cylinder is connected by a line 54 with a port on the valve 413 which, when the spool 42 is in the position shown in Figure 3, will be communicatively connected with an exhaust or fluid return line 55. Hence, fluid in the left-hand end of the cylinder may flow out through line 54 as the pistons 31 and 32 move toward the left.

As soon as the pistons within the cylinder have completed their movement toward the left as viewed in Figure 3, the right-hand arm 44 will engage with the righthand end of the spool 42 and move the latter to the left so as to communicatively connect the branch 52 of the fluid pressure line with the line 54 connected with the left-hand end of the cylinder. Hence, fluid under pressure will be admitted to the left-hand end of the cylinder and pistons 31 and 32 will be urged to move toward the right. At the same time, the line 53 connected with the right-hand end of the cylinder will be comrnunicatively connected with the fluid return line 55 so that fluid may escape from the right-hand end of the cylinder through the line 53. As the pistons 31 and 32 approach their right-hand positions, as shown in Figure 3, the left-hand arm 44 will engage with the left-hand end of the spool 42 and move the piston to the right to the position shown in Figure 3. Thus, the connections to the cylinder will be reversed and the pistons will now be caused to move toward the left end of the cylinder. This reversing operation of the pistons will be repeated so long as fluid under pressure is supplied to the valve 40 through the line 50. Hence, the shaft 26 will be oscillated back and forth and the stones 15 and 16 will be wiped back and forth along the cutting edge of the knife so as to provide a Whetting action thereon.

As shown in Figure 1, it may be found desirable to drench the stones 15 and 16 and the cutting edge of the knife it) with a suitable coolant which may be delivered thereto through a pipe 60.

Having now described my invention in considerable detail and having utilized certain specific terms and language therein, it is to be understood that the present disclosure is illustrative rather than restrictive and that changes and modifications may be resorted to without departing from the spirit or scope of the claims which follow.

I claim:

1. A device for sharpening a rotary knife while the latter is in motion, comprising a shaft mounted for oscillatory motion about an axis parallel to theaxis of rotation of the knife, a supporting member mounted upon said shaft, a pair of arms pivoted at their upper end on said member for movement in a direction transverse to the plane of the knife, a pair of abrasive elements, means for mounting said elements on the lower ends of said arms so that, in the plane of movement of said arms, said elements will lie at an angle to one another, and means for oscillating said member about the shaft axis to cause said abrasive elements to wipe back and forth along the opposite sides of the cutting edge at the same point of the knife as the latter rotates, thereby whetting both sides of the cutting edge simultaneously and maintaining it in a sharpened condition at all times.

2. The device of claim 1 including yieldable means for urging said arms to move about their pivots so as to cause said abrasive elements to be pressed against opposite sides of the cutting edge of the knife.

3. The device of claim 1 in which said oscillating means includes a reciprocating type of fluid pressure motor.

4. The device of claim 3 wherein said oscillating means also includes a reversing valve for said motor, and means for automatically actuating said valve at the end of each reciprocation of said motor.

References Cited in the file of this patent UNITED STATES PATENTS 665,167 Block et al. Ian. 1, 1901 863,956 Waring Aug. 20, 1907 908,129 Pfeifer Dec. 29, 1908 1,130,369 Bortman Mar. 2, 1915 1,815,017 Wagner July 14, 1931 FOREIGN PATENTS 309,637 Great Britain Apr. 18, 1920 

